Viruses have both similarities and differences with other living organisms . One of the features of viruses indicating that they belong to living matter is their need to replicate and create offspring. But, unlike living organisms, the virus cannot survive on its own. It is activated only when it replicates in the host cell , using the host resources and nutrients . When a virus enters a cell, its sole purpose is to make multiple copies of itself in order to infect other cells. Everything he does is aimed at increasing the fitness and number of descendants.
Thus, the virus depends entirely on the host cell [1] . Most viruses are species specific and affect only a narrow host range — plants , animals , fungi, or bacteria .
Content
Infection
As a rule, a viral infection begins when it penetrates the host, namely:
- through physical damage (for example, cuts on the skin )
- by directional injection (for example, mosquito bite [2] )
- directional lesion of a separate surface (for example, inhalation of a virus through the trachea [3] )
Usually, when a virus enters the body, it needs to penetrate into possible sensitive cells.
Virus Penetration
In order for the virus to multiply and thus cause an infection, it is necessary to penetrate into the cells of the host organism and begin to use cellular material. To enter the cell , the surface proteins of the virus bind to specific cell surface proteins. Attachment, or adsorption, occurs between the virus particle and the cell membrane . A hole is formed in the membrane, and the virus particle or only genetic material gets inside the cell where the virus will multiply.
Virus Replication
Then the virus must take control of the cellular replication mechanism. At this stage, a distinction between receptivity and tolerance takes place in the host cell. Tolerance leads to decoupling of the infection. Once cell control is established and its environment is suitable for the virus to start creating its own copies, replication occurs quickly, giving rise to millions of new viruses.
Virus exit
After the virus has created many of its own copies, the cell is emaciated due to the use of its resources. Most of the virus does not need it, so the cell often dies and newborn viruses have to look for a new host. This represents the final stage of the virus life cycle.
Viral latency
Some viruses can “hide” inside the cell. This may be due to avoiding defensive reactions and the host’s immune system , or simply because continuing replication is not in the interests of the virus. This hiding is called latency. During this time, the virus does not give rise to descendants and remains inactive until an external stimulus, such as light or stress , activates it.
Notes
- ↑ NJ Dimmock et al. "Introduction to Modern Virology, 6th edition." Blackwell Publishing, 2007.
- ↑ Bureau for Public Health Division of Surveillance and Disease Control. Dead birds to prevent West Nile, encephalitis viruses. (English) // The West Virginia Medical Journal. - 2005. - March ( vol. 101 , no. 2 ). - P. 90-90 . - PMID 16042095 .
- ↑ Quan FS , Compans RW , Nguyen HH , Kang SM Induction of intranasal immunization. (Eng.) // Journal Of Virology. - 2008. - February ( vol. 82 , no. 3 ). - P. 1350-1359 . - DOI : 10.1128 / JVI.01615-07 . - PMID 18032492 .